Method for making paper yarn



Dec. 12, 1967 c. G. EVANS 3,357,172

METHOD FOR MAKING PAPER YARN Filed Oct. 16, 1964 INVENTOR. CYRIL e. EVANS ATTORNEY United States Patent 3,357,172 METHOD FER MAKING PAPER YARN Cyril G. Evans, Spartanburg, S.C., assignor to Deering Miliiken Research Corporation, Spartanburg, S.C., a corporation of Delaware Filed Get. 16, 1964, Ser. No. 404,355 17 Claims. (Cl. 57165) ABSTRAQT OF THE DISCLOSURE A process for the preparation of a light weight paper yarn which comprises slitting a paper having a basis weight of about eight pounds to about 35 pounds to a width not greater than about A of an inch and then forming a yarn from such slit paper by a folding or twisting operation. The paper has a fiber orientation in the machine direction of at least 80% and an extensibility in excess of 4%. Also, the resulting yarn.

This invention relates to paper yarns and more specifically to light weight paper yarns suitable for the preparation of low cost fabrics.

Paper yarns and the fabrics produced therefrom must, for the most part, be extremely low cost products in order to maintain a competitive position with other textile products. In order to prepare low cost paper yarns and subsequently low cost knit or woven paper fabrics, it is necessary that the paper yarns be light weight yarns, that is to say yarns of not more than about two spindle jute count (yarn of such a weight that a 14,400 yard skein weighs two pounds). Paper yarns of these weights may be produced by slitting light weight papers, that is to say papers having a basis weight (the weight in pounds of a ream of 480 or 500 sheets of paper cut to a given size) of about five pounds to conventional widths of about /2 inch and then twisting or folding. Light weight paper yarns are very expensive, however, and yarns produced from these materials lose their economic advantage. Paper yarns in the aforementioned weight range may be produced if medium to heavy weight papers, to be processed into yarn, are slit to widths of 'less than A inch. Slitting paper to such fine widths will accentuate any defects in the paper in the formation of a yarn and in the subsequent formation of a fabric.

Paper yarns are commonly produced from high wet strength kraft paper by a process wherein slit paper strips are dipped or soaked in water prior to twisting or folding into a yarn. High wet strength kraft papers, however, have an insuflicient degree of flexibility and fiber orientation and when slit strips of such high wet strength kraft paper are twisted, minute tears are introduced into the strip in the twisting operation. In many cases such tears can reduce the strength of the yarn to one-half the strength of the original paper. In addition to the deficiencies of high wet strength kraft paper encountered in twisting operations, high wet strength kraft papers are also found to be lacking in elongation characteristics, a factor which greatly reduces the usefulness of paper as well as the finished yarn product. It is very desirable that a yarn have the ability to resist a sharp blow, that is to say, to elongate to a certain extent and thus absorb the shock rather than breaking.

It is therefore an object of this invention to prepare a fine paper yarn of about two spindle jute count from a medium to heavy weight paper.

It is another object of this invention to prepare a yarn from a high elongation paper.

It is an additional object of this invention to prepare a paper yarn by a process which does not require immersion wetting of the paper.

3,357,172 Patented Dec. 12, 1967 It is still another object of this invention to prepare a twisted paper yarn from a paper having a high degree of fiber orientation.

In accordance with this invention it has now been discovered that a low cost light weight, high strength paper yarn may be prepared by employing a medium to heavy weight paper which is produced by a process wherein the paper web is dried in an unstretched condition. Paper of this type is disclosed in U.'S. Patent 2,624,245 and is known as Clupak (extensible paper marketed by West Virginia Pulp and Paper Company). High elongation paper is usually prepared by drying the paper web in an unstretched condition along the machine direction. For purposes of this invention, however, it is preferred that an isotropic or two-way stretch high elongation paper be employed, that is to say it is preferred that a high elongation paper be employed which is prepared by drying the web in an unstretched condition in both the machine direction and in a direction perpendicular to the longitudinal axis of the paper web. In addition to employing a paper which has been dried in an unstretched condition, it is preferred that the paper also be a paper wherein a substantial quantity of the fibers making up the paper are oriented along the longitudinal axis of the paper web. Best results have been obtained by employing papers wherein in excess of of the fibers were oriented along the direction of the longitudinal axis of the paper web.

The development of high elongation paper is based on two well-known facts: (1) that the impact strength of paper is profoundly influenced by the amount of stretch in the paper and (2) that extra strength can be built into a paper web by control of web dimensions during drying. High elongation paper has greater toughness than ordinary paper, the toughness being achieved by increasing the stretch of the paper in the machine direction from the normal 0.5 to 2.0% to about 13%. The increase in machine direction stretch increases the toughness of a paper such as, for instance normal 50 lb. kraft bag paper from about 55 inches per lb. per sq. in. to about inches per lb. per 100 sq. in. In making high elongation paper, a wet paper web is first pressed against a stretch rubber blanket and then contracted as the rubber blanket is allowed to return to an unstretched condition. This process is accomplished by passing the wet paper web into the nip formed by contacting a rubber blanket with a polished dryer roll. The rubber blanket is stretched considerably at its point of contact with the polished dryer roll. After the rubber blanket passes through the nip formed by contacting the polished dryer roll, the rubber blanket returns to an unstretched condition and contracts slightly from its original state. The wet paper web which is held firmly against the rubber blanket slips on the polished surface of the dryer roll and consequently contracts with the rubber blanket upon losing contact with the dryer roll thereby causing the web to be dried in an unstretched condition in the machine direction.

Fiber orientation in a paper is commonly accomplished by employing a high ratio of Fourdrinier wire speed to stock velocity. A ratio of this type will cause a large proportion of the fibers to be drawn into the machine direction of the paper regardless of the ratio of Fourdrinier wire speed to stock velocity.

It should be understood that high elongation papers may be produced withor without high wet strength characteristics. High elongation wet strength papers are produced in the normal manner, by the incorporation of aldehyde resins, such as for instance urea formaldehyde, melamine formaldehyde and the like, into the pulp prior to sheet formation. These resin additives while increasing the wet strength of paper will often interfere with subsequent dyeing operations and will often render the paper incompatible for laminating operations. As previously mentioned, prior art processes for the preparation of paper yarn require the pa'per to be immersed in water priorto processing, an operation which of course can only be carried out on high wet strength paper. The process employed in this invention; however, does not require immersion of the paper in water and therefore lends itself to the preparation of paper yarns which are free of the high wet strength resin impregnants.

As previously mentioned, it is essential in the prepara tion of a low. cost paper yarn; that the yarn be prepared from finely slit, medium to heavyweight paper. In order to make the preparation of such yarns practical, it is essential that the yarns be processed through twisting operations with aminimum of breaks. It is known that a paper of high extensibility is considerably stronger than comparable papers of low extensibility. Papers prepared according to U.S. Patent No. 2,624,245 having extensibilities of from 4% to 9% have been prepared for use in the preparation of paper yarns. These papers, however, have previously been considered to be of no advantage in that the improved extensibility feature of the paper is lost when the slit paper is processed into yarn. Quite unexpectedly, it has now been found that the extensibility feature which is lost in folding and twisting operations will, in the case of finely slit ribbons, absorb suflicient shock to reduce breaks in ribbon twisting operations in the preparation of low cost yarns. It has also been found that the extensibility feature allows the paper to be processed with less moistening than is employed in previous processes. v 7 l i The yarn of this invention is conveniently prepared by continuously ,moving a web of medium to heavy weight fiber oriented high elongation type paper material, slitting the moving web of paper material into strips, separating the strips, moistening each of the strips and then subjecting the strips. toah operation selected from the group consisting of folding operations and twisting operations. It should be understood that while for commercial operations it is desirable to slit and process a large number of paper strips in a single operation, the novel yarn of this invention mayv also be prepared by twisting or folding a single slit roll or cheese. It is important, however, that slitting operations not remove any extensibility from the paper.

A better understanding of the invention may be had froma discussion of the drawings in which:

FIGURE 1 is a partially schematic drawing of slitting apparatus suitable for the formation of the yarns of this invention.

FIGURE 2 is a partially schematic drawing of twisting apparatus suitable for the formation of the yarns of this invention.

FIGURE 3 is an enlarged illustration of a partially ruptured paper ribbon.

FIGURE 4 is an enlarged illustration of a completely ruptured paper ribbon.

Turning to FIGURE 1 of the drawings an unslit roll of paper 1 is fed through a pair of slitting rolls 2 by a pair of feed rolls 3 to slit the paper roll into a plurality of strips 4. Each of the strips 4 are then wound on a suitable takeup package 5 by means of traverse guide 7 and drive roll 8, the individual strips 4 being kept separate for insuring proper feed to thetakeup package 5 by means of guide pins 6. The paper thus slit to suitable dimensions is then moistened inia manner determined by the physical characteristics of the apparatus being treated and twisted by means of an uptwister as illustrated in FIGURE 2 of thedrawings. In FIGURE 2 of the drawings the bobbin 25 carrying the slit paper is mounted on a whorl 27, the whorl being rotated at speeds in excess of 12,000 r.p.m.s by means of belt drive 28 which is in frictional contact with the whorl 27. Paper ribbon is thereby fed from bobbin member 25 through flier member 26 thereby forming a twisted yarn 30 which is then passed over a traverse guide 31 onto takeup spool 32 which is driven by a suitable drive means such as for instance surface contact roll 33. If desired, a suitable guide means 29 may be disposed between flier member 26 and traverse guide 31. The apparatus of FIGURE 2 is maintained in a high humidity atmosphere, that is to say an atmosphere having a relative humidity in excess of about 70%. Extensible papers free from wet strength imparting resins may be folded or twisted at low speeds under these conditions of high humidity without immersing the paper in water. Where high speed twisting or folding is desired, it is preferred to employ high wet strength extensible paper and to immerse the paper in water and then process into yarn under the high humidity conditions.

Breaks have often occurred in the finely slit papers previously employed, the breaks occurring in the formation of a yarn and especially in the formation of a twisted yarn. Turning to FIGURES 3 and 4 of the drawings, the reasons for the occurrence of these breaks is graphically illustrated. FIGURE 3 is 21 A inch ribbon of 15 lb. kraft paper enlarged twenty times. It can readily be seen that a sheaf of fibers oriented in a direction transverse to the longitudinal axis of the ribbon has produced a weak spot. In order to prevent a complete rupture, it is essential that the ribbon be able to elongate and thus absorb shock during twisting operations. FIGURE 4 of the drawings is a inch ribbon of 15 lb. kraft paper enlarged twenty times. It can be seen that a break was produced due to a slub of fibers being oriented transverse to the longitudinal axis of the ribbon, the few fibers in the area of the slub which were parallel to the longitudinal axis of the ribbon being insufficient to withstand the rupturing shock.

Paper yarns produced in accordance with this invention are suitable for use in weaving or knitting operations for the preparation of fabrics which are specifically suited for low cost applications. More specifically the yarns prepared in accordance with this invention are suitable for use in erosion cloth, carpet backing, knit paper sacks and various plastic laminates.

Having thus disclosed the invention what is claimed is:

1. A process for the preparation of a light weight paper yarn comprising slitting a paper having a basis weight of from about 8 lbs. to about 35 lbs. to a width not greater than A of an inch, said paper having a fiber orientation in the machine direction of at least and having an extensibility in excess of 4%, moistening the slit paper and then forming a yarn by carrying out an operation selected from the group consisting of folding operations and twisting operations.

, 2. The process of claim 1 wherein said paper has a basis weight of from about 15 lbs. to about 28 lbs.

3. The process of claim 1 wherein said paper is a high wet strength paper.

4. The process of claim 3 wherein said paper is a high wet strength paper.

-5. The process of claim 1 wherein said yarn forming operation is a twisting operation.

6. The process of claim 5 wherein said paper has a weight of from about 14 lbs. to about 28 lbs.

7. A process for the preparation of a light weight paper yarn comprising slitting a paper having a basis weight of from about 8 lbs. to about 35 lbs. to a width not greater than /4 of an inch, said paper having a fiber orientation in the machine direction of at least 80% and having an extensibility in excess of 4%, and then forming a yarn by carrying out an operation selected from the group consisting of folding operations and twisting operations in an atmosphere having a relative humidity in excess of about 70%.

3. The process of claim 7 wherein said paper has a basis weight of from about 15 lbs. to about 28 lbs.

9. The process of claim 7 wherein said yarn forming operation is a twisting operation.

basis 10. The process of claim 7 wherein said paper is a high wet strength paper.

11. A process for the preparation of a light weight twisted paper yarn comprising slitting a high wet strength paper having a basis weight of from about 8 lbs. to about 35 lbs. to a width not greater than A of an inch, said paper having a fiber orientation in the machine direction of at least 80% and having an extensibility in excess of 4%, and then dipping the paper in water and forming a yarn by carrying out an operation selected from the group consisting of folding operations and twisting operations in an atmosphere having a relative humidity in excess of about 70%.

12. The process of claim 11 wherein said paper has a basic weight of from about 15 lbs. to about 28 lbs.

13. The process of claim 11 wherein said yarn forming operation is a twisting operation.

14. A process for the preparation of a light Weight twisted paper yarn comprising slitting a paper having a basis weight of from about 8 lbs. to about 35 lbs. to a width not greater than A of an inch, said paper having a fiber orientation in the machine direction of at least 80% and having an extensibility in excess of 4%, said slitting being carried out in a manner so as not to remove the extensibility, immersing said paper in water and then twisting in a manner so as to remove the extensibility at a relative humidity in excess of about 70%.

15. The process of claim 14 wherein said extensibility is in the machine direction and in the direction perpendicular to the longitudinal axis of the paper web.

16. The process of claim 14 wherein said paper has a basis Weight of from about 15 lbs. to about 28 lbs.

17. The product produced by the process of claim 1.

References Cited UNITED STATES PATENTS 2,624,245 I/ 1953 Cluett 162-206 2,896,393 7/1959 Marks 57-165 X 2,955,408 10/1960 Marks 57-32 2,981,052 4/1961 MacHenry 57-154 2,999,788 9/ 1961 Morgan.

3,035,405 5/1962 Welsh 57-165 3,077,723 2/1963 Marks et a1. 57-32 3,168,802 2/1965 Linke et al. 57-140 FRANK J. COHEN, Primary Examiner. J. PETRAKES, Examiner. 

1. A PROCESS FOR THE PREPARATION OF A LIGHT WEIGHT PAPER YARN COMPRISING SLITTING A PAPER HAVING A BASIS WEIGHT OF FROM ABOUT 8 LBS. TO ABOUT 35 LBS. TO A WIDTH NOT GREATER THAN 1/4 OF AN INCH, SAID PAPER HAVING A FILTER ORIENTATION IN THE MACHINE DIRECTION OF AT LEAST 80% AND HAVING AN EXTENSIBILITY IN EXCESS OF 4%, MOISTENING THE SLIT PAPER AND THEN FORMING A YARN BY CARRYING OUT AN OPERATION SELECTED FROM THE GROUP CONSISTING OF FOLDING OPERATION SAND TWISTING OPERATIONS. 